(a) Field of the Invention
An exemplary embodiment relates to a wireless power transmission system.
(b) Description of the Related Art
An electric vehicle may be supplied with power using a wired charging method and a wireless charging method. According to the wireless charging method, an AC electromagnetic field is generated at a primary side (i.e., charger) using an induction coil and a second conduction coil at a secondary side (i.e., electric vehicle) receives power from the AC electromagnetic field generated in the primary side such that a battery of the electric vehicle is charged.
A multi-coil resonator is used to increase efficiency in the wireless charging method. For example, an intermediate coil is added to each of the primary side and the secondary side such that the multi-coil resonator can be formed of four coils. In detail, a source coil and a transmission coil, which is an intermediate coil, may be provided in the primary side and a receiving coil, which is an intermediate coil, and a load coil may be provided in the secondary side. The coils at the primary side and the coils at the secondary side may be symmetrical to each other.
However, the receiving coil, which is the intermediate coil at the secondary side, cannot affect the primary side because the primary side and the secondary side are far from each other. Then, in terms of the primary side, the multi-coil resonator implemented by the four coils operates similar to a multi-coil resonator in which a transmission coil is added only to the primary side and thus implemented by three coils.
In addition, many resistance components are contained in the primary side in wireless power transmission and accordingly a main power loss mostly occurs at the primary side.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.